Standard industrial (20 Amps and above) electrical power/energy meters are often based on current transformers (CT's) for real-time current sensing. An industrial power meter will typically have a CT per load circuit under measurement (e.g. a 3-phase circuit requires three CT's). Load circuits under measurements are inductively applied as the primary side of the CT via the CT's core aperture and the CT's secondary core winding is directly wired to the industrial power meter via a pair of metallic wires. Additionally, an industrial meter will have one potential transformer (PT) per voltage phase being measured. Typically, an industrial facility is a 3-phase electrical environment and therefore three PTs are attached to the industrial power meter to provide associated voltage references for power/energy calculations. The industrial power meter's processing unit calculates active, reactive, and apparent power demand (kW), energy consumption (kW-h), and power factors from the wired CTs (real-time current) and the associated PTs (real-time voltage).
In typical industrial environment, the direct wiring of CTs to the energy meter is problematic and labour intensive. In the electrical facility room, the load circuits to be measured are typically only accessible inside the electrical panelboards, and therefore the CTs have to be installed inside the panelboard. The centralized energy meter is generally installed in the electrical facility room adjacent (i.e. external) to the circuit panelboard. For a large number of CTs, the wiring of CTs from inside the panelboard (via conduits and punch-outs) to an external meter is labour intensive, time consuming, and error prone. The potential exposure of the CT wires, crimps, and screw blocks is also a safety concern in some installations.
The present disclosure of a wireless voltage reference distribution method leads to the design of an industrial CT metering system that eliminates the requirement for any CT panelboard wiring. The elimination of CT panelboard wiring greatly reduces meter installation cost and time. Also, the elimination of CT panelboard wiring greatly reduces the electrical safety concerns of an industrial CT metering installation.